This invention relates to apparatus for processing workpieces (for example semi-conductor wafers) and in particular, but not exclusively, to radial cluster tools.
When manufacturing a semi-conductor device on a semiconductor wafer, it is common to need to process the wafer with successive processes, such as etching and deposition processes, in a common controlled environment, for example under vacuum. It has long been appreciated that considerable savings can be achieved in production time and cost if the chambers can be arranged around a central wafer load/unload station, which itself is kept at the controlled environment, so that the wafers can be passed from chamber to chamber without the need for a vacuum break or the like. Commonly the chambers are arranged so that the wafer transport axis intersect at a common point and such an arrangement is known as a radial cluster tool. One example of such a tool is illustrated in U.S. Pat. No. 5,308,431.
From time to time the processing chambers will require maintenance, for example the replacement of sputtering targets or shielding. In order to allow access for that maintenance, standard SEMI E26-92 of the Trade Body Semiconductor Equipment and Materials International lays down unoccupied or restricted areas which must exist between the footprint of each module or processing chamber. This significantly limits the number of processing chambers, which can be arranged around a load/unload station of particular cross section.
From one aspect the present invention consists in apparatus for processing workpieces in a controlled environment comprising a central workpiece load/unload station having a plurality of processing chambers arranged around the load/unload station so that the workpieces can be moved from one processing chamber to another without leaving the controlled environment, characterised in that:
inlets/outlets of the chambers are radially arranged around the load/unload station;
at least two of the chambers are arranged as an abutting pair; and
maintenance access is provided to each said chamber through its respective non-abutting side and wherein the chamber is substantially fully accessible for maintenance through that access.
In a preferred embodiment the chambers of the pair abut completely. This unequal distribution of chambers enables maintenance access gaps to be provided between pairs and the apparatus includes chambers wherein maintenance access is provided to each chamber through its respective non-abutting side. The chambers are arranged to be substantially fully accessible for maintenance through that access.
It is further preferred that the footprint of each abutting pair and/or the intervening spaces is generally rectangular.
Conveniently, with a normal cross sectional dimension of the loading/unloading station, 6 to 8 processing chambers can be included in the apparatus, the chambers being arranged in pairs.
Preferably the apparatus is in a form of a radial cluster tool in which case the workpiece transport axes may be equally disposed around their point of intersection.
Preferably, a process position of each said processing chamber lies on a circle about a point of intersection of transfer paths to the chambers from the load/unload station.
Although the invention has been defined above, it is to be understood it includes any inventive combination of the features set out above or in the following description.